Through June, the eastern Pacific was warmer than average, but the lack of a strong gradient in sea surface temperature anomalies between the eastern and western Pacific may have kept the atmosphere from getting in sync with the developing El Niño.

Last summer, climate conditions were primed to deliver an above-average—possibly very active—hurricane season in the Atlantic. And then...? The 2013 Atlantic Hurricane season produced the fewest number of hurricanes since 1982. What happened?

The Arctic Oscillation describes simultaneous, geographically “choreographed” shifts in multiple features of the polar vortex: air pressure, temperature, and the location and strength of the jet stream. They all follow the hemisphere-wide oscillation of atmospheric mass back and forth between the Arctic and the middle latitudes, sort of like water sloshing in a bowl.

A few days of unusually cold weather in the U.S. and Canada aren't a sign that a century-or-more trend of rising global surface temperatures has reversed itself. In fact, the cold wasn't even all that widespread for the Northern Hemisphere.

Meteorologists have known for years that the pattern of the polar vortex determines how much cold air escapes from the Arctic and makes its way to the U.S. during the winter. Climate scientists are wondering if a warmer Arctic could explain its odd behavior in recent years.

October in Alaska this year was more like September, with warmth and rain in place of autumn chill and snow. Wind anomalies related to unusual pressure patterns conspired to bring a steady stream of warm, wet air from southerly latitudes into Alaska.

Maps of the thousands of storms that have passed through the Eastern Hemisphere tropical oceans in the past century or so reveal a more crowded landscape than similar maps of the Western Hemisphere. Unlike the Western Hemisphere, where storms are mostly confined to areas north of the equator, the Eastern Hemisphere sees storms in both north and south tropical waters.